When Amy Bloom writes, she tends to hear things before she can see them. For example, the title of her second collection of stories, A Blind Man Can See How Much I Love You, was something an old boyfriend had said to her, so sweet and well phrased she suspects it prolonged the doomed relationship. In "Your Borders, Your Rivers, Your Tiny Villages" a woman observes that her husband and his friend "talk like they've just come from a meeting with the Joint Chiefs of Staff". They are white-collar workers, watching TV news, in the US equivalent of Surrey. "It's either a first sentence," says Bloom, "or it's a little conversation between two people, and then suddenly I know who's saying it. I hear the speaker and then I see the character and then I see the story."

The men in the living room with their important opinions open her third collection, Where the God of Love Hangs Out, which sounds like a Judy Blume novel but is a decisively grown-up compilation of two quartets and four stand-alone pieces. It is a strange assortment, held together by Bloom's unerring tone: sharp, dark, flatly hilarious, full of crises revisited which, with a chiropractic snap, are put into sudden perspective by those who have suffered them. There are the small transgressions – a teenager who paints a picture of the crucifixion on her trouser leg ("I'm not mocking Jesus," I told my mother. "I'm just representing him, on my jeans") – and the large ones: a woman who has slept with her own stepson, an old bully with Alzheimer's who throws things at his family. All are recounted with restraint and brevity. A man called William says to his wife, "darling, you are as clear and bright as vinegar but not everyone wants their pipes cleaned". It's a sentiment that might apply to the author, who, on a freezing day in Connecticut, poses gamely in a blizzard and issues a friendly warning to the photographer: that in photos she tends to go one of two ways, OK or George Foreman.

Before she became a full-time writer Bloom, 56, worked for 20 years as a psychotherapist, which to her irritation and amusement is sometimes regarded as a form of cheating when it comes to her fiction. If there is anything psychotherapy teaches you, she says, it is that people's hang-ups are profoundly, non-transferably, tediously specific. She was not terribly concerned with how or why her clients came to be the way they were, although, she says drily, "it may have been interesting to them". It is more the case, she explains, "that you say to them 'you seem to be carrying this little tin can left over from 1964 with you everywhere you go; maybe you'd like to put it down?' And sometimes they go, no, it's way too hard to put it down, I would like to ruin my relationships for the rest of my life, thank you very much. And you go OK, see you around." In terms of her fiction, the approach translates into: "if you've done a good job of presenting the character, people can hear him and see him and you don't have to go into a lot of blah blah blah about how he came to be. It's mostly misleading and pointless."

Bloom's philosophy – easy on the blah blah blah – is most emphatically illustrated in her second novel, Away, published in 2007 to critical acclaim and bestsellerdom. It's a slim volume, but one that could have been 1,000 pages long, a classic immigrant tale of a woman escaping the pogroms in Russia to make a new life for herself in New York and her subsequent odyssey across the States in search of her daughter. It was widely compared to EL Doctorow's Ragtime, and a reminder of how few novels of this kind – the great journey west – feature women protagonists. Bloom's aim was to take the 19th-century epic and infuse it with a modern novelist's concern with interior life. In the case of Lillian, the heroine, it's a frozen landscape, her "dead American self" she calls it, but like most of Bloom's heroines she is wryly aware of how others see her ("doomed, foolish and peculiar").

"I hope," Bloom says, "I will never write a 1,000-page novel. I hope I'll never write even a 700-page novel. Not that some people don't do those wonderfully. But a lot of the riffs and balloons that get set off in those long novels are just not to my taste."

She was in her mid-30s when she started to write, her 20s having been spent raising three children and working fulltime. She would write late at night and first produced a mystery novel, which, after it was accepted for publication, she bought back because she didn't think it was good enough. Come to Me, her first collection of stories, was shortlisted for a National Book award. It opened with the kind of unsettling non sequitur – "In the middle of the eulogy at my mother's boring and heart-breaking funeral, I began to think about calling off the wedding" – that launches many of Bloom's stories, usually successfully, occasionally hammily ("I had always planned to kill my father") but that in any case announced she meant business.

In an era of withering attention spans, it's surprising that short stories aren't in greater demand. It's a question of commitment, Bloom says. "There is a big category of not very well-written but extremely readable novels – books you take to the beach, to the airport, the genre novels that don't require much of you but fill a few hours. There are very few short stories like that: big, badly written, eminently readable. Those novels require absolutely nothing. It's like watching television." Even the literary magazines she writes for reject stories that have more than one strand. "The short story in the modern magazine is an extended anecdote."

Cod-psychologists might suggest that Bloom started writing late because both her parents were employed as writers: her mother for magazines, which she gave up after having children and her father as a financial journalist. They lived in a privileged part of Long Island, outside New York, and by her own definition Bloom was a weird little creature, running around shouting new words she'd learnt and when asked what she'd like for her ninth birthday answering "my own apartment". But the writing her parents did had no discernible effect on her, she says. "My father never spoke about his work. He was pretty workmanlike – no one was ever going to say, boy, I remember that great sentence. It was more like living with a hardworking carpenter or something. It wasn't like my father was Harold Pinter."

The benefit of having writers in the house was that she was encouraged to read and ploughed through all the 19th-century novels that her father avoided. He did not read fiction, to the extent that she doubts he even read her books. "He was a difficult man," she says, although he was proud of her. She sees echoes of his truculence in her own habits. Bloom doesn't read reviews, for instance, something that comes from her father. "His basic position was you don't want to give other people power over you. You want to do what you think is right and what matters to you, and if other people don't like it, as my father would have said, they can go fuck themselves."

Isn't there anything to be gained from reading other people's opinions about you? She considers. "I don't think I've ever met a writer who felt that they had actually learnt something from a review. I think that's been consistently true since, like, Boswell. Also, I read my work pretty stringently."

That stringency is hard to square with her career in psychotherapy, which must, surely, have involved listening to people talk endlessly about themselves, as Bloom's characters are not permitted to do. "Right!" she says. "Which is why when people say, did being a therapist help you become a writer, I say, no. Not really – although learning to listen to people is certainly a good thing if you're going to write, as well as learning to shut up so they can finish their sentence." She had strong ideas about the limitations of therapy. Would she ever tell a client to snap out of it? "Well, for example, if someone has been spending three hours over the course of three weeks speaking about their Yorkshire terrier's breathing difficulties, at some point I might say" – she smiles dangerously – "that's a lot of time about the Yorkie. And if that doesn't move them, I might say something like, you know, sometimes people are aggressively boring because they don't want to talk about what's on their mind."

That's a tough approach. "Yeah, I know." She shrugs. "I liked being a psychotherapist. I felt it was something I was good at because I find people interesting, not because I have an overwhelming sense of love and kindness and compassion. I do feel compassion, because we make such terrible mistakes and are constantly running into walls and going, arrrgh – a wall! But I also find them interesting."

She hasn't been surprised by the amount of interest there has been in her personal life. From the age of 13 she knew she was bisexual, and after her first marriage ended she lived with a woman for some time. "I'm sure it's interesting to people." She smirks at the understatement and understates the case herself: "Being surprised," she has said, "that there are people in the world who are genuinely attracted to men and women is to me a little bit like being surprised that there are people who like chicken and salad." During the gay years did she sense her work being subtly repositioned in the marketplace? "Well, it wasn't that I thought, oh now I'm going to spend the rest of my life on the gay bookshelf; I didn't really care. Also I thought, if I'm good, I won't just be on that bookshelf and if I'm not so good I'll be on that bookshelf along with memoirs about having cystic fibrosis and growing up in New Guinea." She is married again now and has been more or less dropped by the interest groups that sought her patronage. She smiles. "I'm dull as houses."

Her husband is an architect, which suits her perfectly; he has a good eye and understands from his own work that "staring out of the window does not mean you're not doing anything." The idea of living with another writer makes Bloom shudder. "I'd rather be married to a sanitation engineer, or a guy who ran a fancy food emporium or someone who transforms live organ transplants." Why marry rather than live together? "We got married because we're not the kind of people who get tattoos. We were so stunned to find ourselves so smitten, so late, that there seemed to be some sort of ritual you could go through to celebrate it, and it turned out there was."

Bloom did, eventually, find some artistic use for her first career, as the backdrop for a TV series she wrote and co-produced called State of Mind. It ran in the US in 2007 and was set in a psychotherapy practice where the therapists were neither loathsome, ridiculous nor god-like. Producing, she says, is a piece of cake if you have raised children and held down a job. More screenwriting offers came her way, including a Francis Ford Coppola project starring Barbra Streisand, which, in the preliminary meetings before it fell through, she describes as being like "Godzilla meets Frankenstein, and I was played by the city of Tokyo". Screen work is only a sideline, something she escapes to periodically from the "well" of novel-writing. "The good news [about TV and film] is that you have other people to play with and the bad news is that you have other people to play with."

Although her first novel, Love Invents Us, and Normal, a non-fiction book of interviews with transsexuals that she wrote after doing some professional work in the area, were both well received, it was the success of Away that promoted Bloom into another league. Now, she says, "I get 30 people at a reading instead of nine." The book takes place in the aftermath of a massacre but is, fundamentally, optimistic, "about creating some happiness in a painful life. I wanted to write about people going on, after terrible loss."

Much of the joy of her work is in the accuracy of the images: in the new collection, a woman has legs with "hard calves that squared when she moved"; a child running about "is a lovely thing to watch, the way gravity barely holds him". The close-ups of the body seem almost clinical – a word she rejects, "but I know what you mean; which is that they are not always filled with an obvious emotion. The body interests me all the time, in birth and death and sex. I feel like it's one of those objects that you can't beat, both as the thing itself and as a metaphor. It's kind of a big garden." The only drawback, perhaps, is the characters' relentlessly sardonic interior voices ("what kind of woman wears a toe ring? Frances thought"), which get a little wearing and blur into one.

Bloom's friends sometimes tell her that she is funnier in person than in prose, although there is, she believes, no escaping the fundamentals of who you are in your writing. "Nobody reads Philip Roth and thinks, what a sweet lovable old coot, I'd love to introduce him to mom." Dark humour is so deep in her nature it informs everything she does, along, she says, with her refusal to compromise. Her mystery novel is as yet unpublished. She shrugs. "I take it pretty seriously. I think if it's not good, don't publish it."